Certain dietary carbohydrates promote Listeria infection in a guinea pig model, while others prevent it.

It has been proposed that dietary non-digestible carbohydrates can improve host resistance to intestinal infections by stimulating health-promoting bacteria in the gut. However, evidence from in vivo infection studies is scarce, particularly for gram-positive infections. We studied the effect of five non-digestible carbohydrates on the resistance of guinea pigs to Listeria monocytogenes infections. Animals were fed a diet supplemented with 10% xylooligosaccharides (XOS), galactooligosaccharides (GOS), inulin, apple pectin or polydextrose for three weeks before oral infection with a mixture of three different fluorescently labeled L. monocytogenes strains. Colonisation of L. monocytogenes in the intestine was determined by quantification of L. monocytogenes in faecal, ileal and caecal samples while translocation was determined by quantification of L. monocytogenes in mesenteric lymph nodes, spleen and liver. XOS and GOS significantly (P<0.05) improved the resistance of guinea pigs to L. monocytogenes, while inulin and apple pectin decreased the resistance (P<0.05). No significant effect on resistance to L. monocytogenes was seen after feeding with polydextrose. No difference in caecal weight or pH between the dietary groups was measured, except for a higher caecal weight and a lower caecal pH of animals fed with XOS, and a lower caecal pH for animals fed with polydextrose. In conclusion, this study shows for the first time that different non-digestible carbohydrates can have entirely different effects on the intestinal colonisation and translocation of a pathogenic bacterium.